Function chaining depending on boolean result

Question

This is just an efficiency question really.. I'm interested to know if there is a more efficient or logical way that people use to handle this sort of scenario.

In my asp.net application I am running a script to generate a new project my code at the top level looks like this:

Dim ok As Boolean = True
    ok = createFolderStructure()
    If ok Then ok = createMDB()
    If ok Then ok = createProjectConfig()
    If ok Then ok = updateCompanyConfig()

I create a boolean and each function returns a boolean result, the next function in this chain will only run if the previous one was successful. I do this because an asp.net application will continue to run through the page life cycle unless there is an unhandled exception and I don't want my whole application to be screwed up if something in the chain goes wrong (there is a lot of copying and deleting of files etc.. in this example).

I was just wondering how other people handle this scenario? the vb.net single line if statement is quite succinct but I'm wondering if there is a better way?

Answer 1

Normally, a function should not return true/false based on its result - that is considered old fashioned. A try/catch block is better here, where the function throws an exception in case of an error. That is, of course, assuming errors only occur at special occasions:

Try
    createFolderStructure()
    createMDB()
    createProjectConfig()
    updateCompanyConfig()
    ''// ...
Catch ioExeption as IOException
    ''// handle it
End Try

Answer 2

You could drop the Boolean all together

If createFolderStructure() Then
If createMDB() Then
If createProjectConfig() Then
If updateCompanyConfig()

but I have to agree that using exceptions is the better way to handle these situations.

Answer 3

Kobi showed you the way to do it. If you really need to use the results of boolean functions then you can chain them with the AndAlso operator.

Dim ok As Boolean
ok = createFolderStructure() 
    AndAlso createMDB()
    AndAlso createProjectConfig()
    AndAlso updateCompanyConfig()

Those expressions are evaluated lazily, i.e. if one function returns false the rest of the expression is not evaluated.